In many high density computer system installations, the computer systems are mounted in racks, which are in turn arranged in repeating rows or cells. As the densities of these computer systems have increased, the need for improved cooling systems for dissipating heat generated by the computer systems has increased as well.
FIG. 1 is a perspective view of an existing rack-mounted computer system 100. The computer system 100 comprises a chassis 102 containing a motherboard 104 and the various components of the computer which are coupled to the motherboard 104, such as one or more CPUs (central processing unit), memory, one or more hard disk drivers, and a power supply 110. The top cover of the chassis 102 is removed in FIG. 1 for clarity. In this example, the front side of the computer system 100 includes a variety of I/O (input/output) ports 112 and air intake ports 116 to allow cooling air to enter the chassis 102. The back side of the computer system 100 includes a plurality of fans 114 for drawing air out of the chassis 102.
The back side of the power supply 110 is positioned adjacent the back side of the chassis 102, and an opening is provided in the back side of the chassis 102 to expose the power plug receptacle and power switch of the power supply 110. The front side of the power supply 110 includes an air intake port 120 to allow cooling air to enter the power supply 110. The back side of the power supply 110 includes an air exhaust port (not shown) and a fan for drawing air into the air intake port 120 and out of the exhaust port. The back side of the chassis 102 also includes an opening to expose the exhaust port and the fan so that the cooling air drawn through the power supply 110 is exhausted out of the back side of the computer system 100.
In a standard installation, the computer system 100 is mounted with similar computer systems and other electronic equipment in a rack assembly. A standard rack that is widely used measures roughly 19 inches wide, 30 inches deep and 74 inches high. These racks may be arranged in rows of, for example, roughly 10-30 units, with access doors on each side of the racks. Access aisles are provided on both sides of the rows so that an operator may approach the access doors on each side.
In conventional rack-based computer systems, a plurality of computers are supported in a single stack in a rack. The front door of the rack assembly provides access to the front sides of the computers and the back door provides access to the back sides. Each computer system may also include one or more fans that draw ambient air into air intake ports provided on one side of the computer system, through the computer chassis, and out of exhaust ports provided on the opposite side of the computer system. The ambient air passing through the computer systems is used to cool the various components contained within the computer chassis.
In this type of installation, the computer systems are arranged such that the back sides of each row of computer systems face the back sides of an adjacent row of computer systems, and the front sides of each row of computer systems face the front sides of an adjacent row of computer systems. As a result, the rows of racks form “hot aisles” and “cold aisles”. This arrangement enables cool air to flow from an HVAC system through the cold aisles to the front air intake of the computer systems. The heated air emitted by the computer systems flows away from the back exhaust to the air conditioner return ducts. This layout reduces the transfer of hot exhaust air from one system into the intake air of another system.
In another type of arrangement, two stacks of computer systems are positioned in a single rack in a back-to-back arrangement. An exhaust air plenum is provided between the two stacks of computer systems for allowing the exhaust air to be directed upward and away from the rack. An example of this arrangement is described in U.S. Pat. No. 6,496,366, entitled, “HIGH DENSITY COMPUTER EQUIPMENT STORAGE SYSTEM,” the disclosure of which is incorporated by reference herein in its entirety.
In either arrangement, by drawing the heated air out of the computer system 100 and into the aisle or plenum, the exhaust fans 114 may produce a negative pressure within the chassis and a positive pressure immediately outside of the back side of the computer system. Accordingly, in order for the fan in the power supply 110 to effectively draw air through and out of the power supply 110, the fan must be strong enough to overcome the differential pressure between the inside and the outside of the computer system. This may be accomplished by using a higher power fan, but that can consume an excessive amount of the power supplied by the power supply 110. If the pressure differential of the computer system and the exterior region is sufficiently high, the power supply fan may be prevented from blowing heated air out of the back of the chassis or the heated air that had been emitted out of the computer chassis may even flow back into the power supply through the power supply fan opening, thereby causing the power supply to overheat and fail.
Accordingly, there is a need for an improved method of cooling a power supply for a computer system.